iommu/vt-d: Use INVALID response code instead of FAILURE

The VT-d IOMMU response RESPONSE_FAILURE for a page request in below
cases:

- When it gets a Page_Request with no PASID;
- When it gets a Page_Request with PASID that is not in use for this
  device.

This is allowed by the spec, but IOMMU driver doesn't support such cases
today. When the device receives RESPONSE_FAILURE, it sends the device
state machine to HALT state. Now if we try to unload the driver, it hangs
since the device doesn't send any outbound transactions to host when the
driver is trying to clear things up. The only possible responses would be
for invalidation requests.

Let's use RESPONSE_INVALID instead for now, so that the device state
machine doesn't enter HALT state.
Suggested-by: Ashok Raj <ashok.raj@intel.com>
Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com>
Link: https://lore.kernel.org/r/20210126080730.2232859-3-baolu.lu@linux.intel.comSigned-off-by: Joerg Roedel <jroedel@suse.de>

drivers/iommu/intel/svm.c

@@ -911,10 +911,8 @@ static irqreturn_t prq_event_thread(int irq, void *d)
 		u64 address;
 
 		handled = 1;
-
 		req = &iommu->prq[head / sizeof(*req)];
-
-		result = QI_RESP_FAILURE;
+		result = QI_RESP_INVALID;
 		address = (u64)req->addr << VTD_PAGE_SHIFT;
 		if (!req->pasid_present) {
 			pr_err("%s: Page request without PASID: %08llx %08llx\n",
@@ -952,7 +950,6 @@ static irqreturn_t prq_event_thread(int irq, void *d)
 			rcu_read_unlock();
 		}
 
-		result = QI_RESP_INVALID;
 		/* Since we're using init_mm.pgd directly, we should never take
 		 * any faults on kernel addresses. */
 		if (!svm->mm)